Abstract: A signal processing circuit includes a first circuit coupled between a power terminal and a first ground terminal and a second circuit coupled between the power terminal and a second ground terminal. The signal processing circuit is configured to receive a first signal at a voltage level relative to the first ground terminal and, in response to the first signal, provide a second signal at a voltage level relative to the second ground terminal. The signal processing circuit can be used in a battery protection circuit for a mobile device having an embedded battery. The battery protection circuit is configured with two NMOS transistors to allow the cell phone circuit to switch between the embedded battery and an external power source.

Abstract: A driver circuit for an LED (light-emitting diode) lamp includes a transformer having a primary winding and a secondary winding, a dimmer circuit coupled to a power source for varying an input voltage to the primary winding, and an output rectifying circuit coupled to the secondary winding for providing an output current to the LED lamp. The driver circuit also includes a controller coupled to the dimmer circuit to receive an average input voltage signal (DIM) from the dimmer circuit. The controller is configured to vary the output current according to the average input voltage.

Abstract: A bleeder circuit is provided in a switched mode power supply (SMPS) that provides a compensation current when the loop current drops below the holding current of the TRIAC to alleviate light flickering problem. Further, automatic power factor correction is also provided in embodiments of the invention, which enables the output current to be in phase with the input voltage. The power factor correction not only improves the efficiency of the power supply, it can also reduce the compensation current and the duration in which compensation current flows, thereby reducing the power loss in the bleeder circuit.

Abstract: A control circuit is provided for a buck converter that includes at least an inductor coupled to an output of the buck converter. The control circuit includes a power switch configured for coupling to a line voltage and configured for charging the inductor, an input line voltage sampling circuit, and a constant-voltage (CV) and constant-current (CC) control module coupled to the power switch. During a charging period of the inductor, the CV and CC control module is configured to control the power switch to provide a constant output current by maintaining a constant peak inductor current, even when the input line voltage changes. During a discharging period of the inductor, the CV and CC control module is configured to monitor the sensed output voltage to control the power switch to provide a constant output voltage.

Abstract: A power supply controller is provided for providing a drive current to a control terminal of a power transistor in three time intervals. The controller includes control circuits configured to control the drive current in multiple stages. During a first time interval, first drive current includes a current spike for turning on the power transistor in response to a start of the control signal pulse. During a second time interval, a second drive current includes a ramping current substantially proportional to a magnitude of a current through the power transistor. During a third time interval, current flow to the power transistor is at least partially turned off before an end of the control signal pulse.

Abstract: A switching mode power supply (SMPS) includes a transformer having a primary winding for coupling to an input power source, a secondary winding for providing an output voltage of the SMPS, and an auxiliary winding. The SMPS also has a power transistor coupled to the primary winding and a primary side control circuit coupled to the auxiliary winding and the power transistor. The primary side control circuit is configured to regulate the output of the SMPS by controlling the power switch in response to a feedback voltage signal that is representative of an output of the SMPS. The SMPs also has a secondary-side control circuit coupled to the secondary winding and being configured to cause the output voltage of the SMPS to discharge when the output voltage of the SMPS is higher than a first reference voltage.

Abstract: A chopper amplifier circuit for sensing Hall voltage with reduced offsets includes a Hall sampling circuit with a first switching circuit for selectively coupling each of four nodes of a Hall plate to either a power source or a ground terminal. The circuit also includes a differential amplifier and a second switching circuit configured for selectively coupling each of the four nodes to inputs of the differential amplifier. A Hall voltage signal retaining circuit includes two groups of four storage devices and a second group of four storage devices. A third switching circuit is configured for outputs of the differential amplifier to selected ones of the storage devices. A fourth switching circuit is configured for selectively coupling the storage devices outputs of the chopper amplifier circuit.

Abstract: A controller for a switched mode power supply (SMPS) is provided. The SMPS is equipped with a transformer having a primary side winding, a secondary winding, and an auxiliary winding. The controller includes a detection circuit for detecting a transition from a first output load condition to a second output load condition of the SMPS and a control circuit coupled to the detection circuit and being configured to output one or more control signals in response to the detected output load transition. Depending on the embodiment, the one or more control signals include a first control signal for turning on a power switch to cause a current flow in a primary winding of the SMPS and/or one or more second control signals for turning off one or more functional circuit blocks in the controller.

Abstract: A switching mode power supply (SMPS) includes a rectifying device configured for converting a periodically varying input AC (alternating current) voltage into a DC (direct current) voltage, and a transformer including a primary winding, a secondary winding, and an auxiliary winding. The primary winding is coupled to the rectifying device. An input capacitor is coupled to the rectifying device and the primary winding of the transformer. A first power switch is coupled to the input capacitor. A control circuit is coupled to the first power switch and is configured to control the first power switch based on a phase or amplitude of the input AC voltage. By controlling the charging and discharging of the input capacitor, power is provided to the primary winding during a longer portion of the AC input voltage cycle, allowing the rectifier device to have a larger conduction angle to increase a power factor (PF).

Abstract: A pulse frequency modulation (PFM) controller for controlling a switching mode power supply. The controller includes an output terminal for providing a control signal to turn on and off a current in the power supply to regulate an output of the power supply. A first input terminal receives a feedback signal related to the output of the power supply, the feedback signal exhibiting a ringing waveform when the current in the power supply is turned off. The controller also includes a control circuit configured to provide the control signal in response to the feedback signal. The control signal is adapted to turn on the current in the power supply when the feedback signal is substantially at a valley of the ringing waveform of the feedback signal. In an embodiment, such a PFM controller can reduce turn-on transition loss in a power supply and provides frequency dithering to reduce electromagnetic interference.

Abstract: A control circuit is configured for controlling a power switch to regulate an output of a power converter. The control circuit is configured to increase a switching frequency of the power switch when a first signal representing a magnitude of the power converter is below a first output level. In some embodiment, the first output level is selected such that when the first signal is below the first output level, the power converter may generate audible noise. In an embodiment, when the first signal is above the first output level, the control circuit is configured to turn off the power switch when a second signal representing a current in the power switch is above a first reference level. On the other hand, when the first signal is below the first output level, the control circuit is configured to turn off the power switch if the second signal reaches a lower reference level.

Abstract: A system for driving an LED (light-emitting diode) lamp includes a dimmer circuit coupled to a line input voltage for varying a magnitude of an input voltage and a transformer having a primary winding, a secondary winding, and one or more auxiliary windings, the primary winding coupled to the dimmer circuit. The system also includes an output rectifying circuit coupled to the secondary winding for providing an output current to the LED lamp and a power switch coupled to the primary winding for controlling a current flow in the primary winding. The system further includes a controller having a comparator and a capacitor for providing a control signal to control the power switch for regulating the output current.

Abstract: A synchronous rectification circuit for a power supply includes a power switch for coupling to a secondary winding of a transformer of the power supply and an output capacitor of the power supply. The power switch includes a four-terminal MOSFET having a source, a drain, a gate, and a body. A body diode is formed by a junction between the body and the drain or by a junction between the body and the source. The body diode is coupled in parallel to the source and drain of the power transistor. A control circuit is configured to provide a control signal for controlling an on/off state of the power switch in response to a voltage condition of two terminals of the power switch. When the body diode makes a transition from reverse bias to forward bias, the control circuit causes the MOSFET to turn on, and when the forward bias voltage drops below a reference voltage, the control circuit causes the MOSFET to turn off.

Abstract: A switching mode power supply (SMPS) includes a power transistor coupled to the primary winding of transformer and a resistor coupled between the input power source and a control terminal of the power transistor for triggering a primary current flow through the power transistor for providing startup power. A primary side control circuit is configured to regulate the output of the SMPS. A secondary side control circuit is coupled to the secondary winding and being configured to provide a first electrical signal to the secondary winding when an output voltage of the SMPS is less than a first reference voltage, whereupon an awakening signal is induced in the auxiliary winding and causes the primary side control circuit to provide a turn-on signal to the power transistor. The primary side control circuit is configured to enter a standby mode or a normal operating mode in response to the awakening signal.

Abstract: An apparatus for coupling a switching mode power supply (SMPS) controller to a rectified line voltage. The apparatus includes a high-voltage startup transistor configured to provide a charging current during a startup phase of the SMPS controller and to provide substantially no current during a normal operation phase of the SMPS controller. A switch coupled to the high-voltage startup transistor. The switch receives a control signal from the SMPS controller, for turning off the switch during the startup phase and turning on the switch during the normal operation phase. A biasing device is connected in series with the switch and maintains the startup transistor in an off state when the SMPS controller is in the normal operation phase. A standby current in the apparatus is substantially lower when the SMPS controller is in the normal operation phase than the charging current in the apparatus when the SMPS is in the startup phase.

Abstract: The present invention relates to a system and method controlling motor rotation speed and provides a cooling system and method configured to control a temperature associated with an integrated circuit. The cooling system includes a brushless motor, a temperature monitoring input, a clock input, and a motor controller.

Abstract: A switching mode power supply (SMPS) includes a transformer having a primary winding for coupling to an input power source, a secondary winding for providing an output voltage of the SMPS, and an auxiliary winding. The SMPS also has a power transistor coupled to the primary winding and a primary side control circuit coupled to the auxiliary winding and the power transistor. The primary side control circuit is configured to regulate the output of the SMPS by controlling the power switch in response to a feedback voltage signal that is representative of an output of the SMPS. The SMPs also has a secondary-side control circuit coupled to the secondary winding and being configured to cause the output voltage of the SMPS to discharge when the output voltage of the SMPS is higher than a first reference voltage.

Abstract: A startup circuit for a switching-mode power supply (SMPS) includes a first voltage detector configured to trigger the switching-mode power supply from a first operation mode to a second operation mode when an input supply voltage exceeds a first threshold voltage, a current consumption in the first voltage detector in the first operation mode being determined by a reverse leakage current of a diode. A feedback circuit is coupled to the first voltage detector and being capable of maintaining a positive feedback loop. A second voltage detector is coupled to the first voltage detector and the feedback circuit, and is configured to trigger the switching-mode power supply to switch from the second operation mode to the first operation mode when the input supply voltage is below a second threshold voltage.

Abstract: A current control circuit includes an input circuit for receiving an input signal, an output circuit for providing an output signal. The output circuit is coupled to the input circuit to receive a current therefrom. The current control circuit also includes a feedback circuit coupled to the input circuit and the output circuit to form a feedback loop. The current control circuit further includes a first slope compensation current coupled to the output circuit for controlling the output signal, the first slope compensation current being a periodic current. The current control circuit also includes a second slope compensation current coupled to the feedback circuit, wherein the second slope compensation current has the same phase and period as the first slope compensation current.

Abstract: A switching mode power supply (SMPS) includes a transformer having a primary winding, a secondary winding for providing an output voltage, and an auxiliary winding. The SMPS also includes a power switch coupled to the primary winding. A first control circuit is coupled to the secondary winding, and is configured to provide a first electrical signal to the secondary winding when the output voltage of the SMPS is less than a reference voltage during a discontinuous time, whereupon a second electrical signal is induced in the auxiliary winding. A second control circuit is coupled to the auxiliary winding and the power switch. The second control circuit is configured to regulate the output of the SMPS by controlling the power switch in response to a feedback voltage signal from the auxiliary winding, and is further configured to turn on the power switch in response to the second electrical signal.